Henry cor



Jan. 0, 1925. 1,523,404

H. CORMACK RADIO TUNING DEVICE Filed Aug. 27. 1923 Patented Jan. 2!), 1925.

UNITED STATES HENRY COR-MACK, CF QUINCY, MASSAGHUSETTS.

RADIO TUNING DEVICE.

Application filed Augu t .27, 1923. Serial No. 659,50.

To all whom it may concern.

Be it known that I, HENRY CORMAGK, a citizen of the United States, residing in Quincy, in the county of Norfolk and State of Massachusetts, have invented an Improvement in Radio Tumng Devlces, of whlch the following descrlption, in connection with the accompanying drawings, is a specificaof novel and improved construction by whlch extremely exact and sensitive tunlng may be obtained, and which in addition is of a simple and durable construction.

To this end, the tuning coil comprises awire bent to form a coil and preferably a plurality of coils, and having pro-vision for connection to one point in the circuit to be tuned, and a contact member capable of connection to asecond point in the circuit, and arranged to bear upon the wire of the coil or coils and to move lengthwise thereof around the coil 'or coils, the contact member and the coils being arranged to be capable of relative rotary movement to permit the contact member to bear upon successive portions of each coil. In the preferred form of the invention the wire is helically wound about an insulating tube rotatably mounted in suitable supporting members at its opposite ends and the contact memberis mounted upon av pivoted arm arranged to permit the contact to move transversely across the successive coils of the wire as the tube is rotated, and to continuously bear against the wire of successive coils.

These and other features of the invention will be hereinafter described and particularly pointed out in the claims at the end of fit over the wire of each coil 10, and in windthis specification.

In the drawings illustrating the preferred embodiment of the invention, Fig. 1 is a side elevation of the improved tuning coil;

Fig. 2 is a front elevation of the same;

Fig. 3 is a vertical section through the axis of the drum shown in Fig. 1; and

Fig. 4 is an enlarged detail illustrating the construction of the pivoted contact arm.

Referring to the drawings, the improved tuning coil comprises a turn or coil of wire 10, and preferably a plurality of coils arranged tobe capable of connection at one point 12 in the circuit to be tuned, and a contact member 14 arranged to bear upon the wire of the coil or coils and itself capable of connection to a second point 15 in the circuit to be tuned. The coil or coils of wire 10 and the contact member 14 are arranged to be capable of relative rotary movement so as to permit the contact member to be moved lengthwise of the wire comprising each turn or coil 10 upon the relative rotary movement of the coils and contact member, and in this manner to permit contact to be made at all points in each coil, thus securing an exact and sensitive tuning of the circuit.

As hereln shown, a bare wire is wound in the form of a helix upon an insulating tube or cylinder 20 provided with end members 21 of insulating material. The helix may be provided with any desired number of coils 10. Each end member 21 is provided with a bolt 22 projecting outwardly through a hole therein, and a lock nut 23 for securing the bolt 22 in fixed relation to the end members 21. The ends of the bolts 22 are preferably tapered and journaled in cone shaped bushings 25 fitted in and secured to metal supporting brackets 26 aflixed to a support ing piece 27 of insulating material forming asupporting base upon which the tuning coil is mounted. One end 28 and preferably both ends 28 29 of the wire comprising the coils 10 are soldered to the bolts 22, as illustrated in Fig. 3, to provide a fixed electrical connection between the coils and the metal supporting brackets 26. One of the metal supporting brackets 26 is connected with a binding post 30 by a wire 81 extended beneath a'portion of the insulating supporting piece or base 27 as illustrated in Fig. 1. The movable contact member 141 may and preferably will comprise a metal point or finger 33 provided with a groove 35 in the end thereof to permit the said pointor finger to ing the coils upon the insulating cylinder or I 33 to engage each coil straddling the wire without coming in contact with the wire of adj acent coils. The metal point or finger 83 comprising the contact member may and preferably will be mounted upon the end of the arm 14: pivotally mounted upon the supporting piece or base 27 to be capable of a movement toward and from the supporting drum or cylinder 20 and also lon it thereof. As herein shown, the pivoted arm 14 is curved upwardly over the drum or cylinder 20 to cause the metal point or finger 33 to bear at substantially the top of the coils. The contact arm 14 is herein shown as pivoted at in the forked end of a collar 46 which bears upon a washer 4'? resting upon the top of an insulating block 48and held in position upon the block by a screw 50extended downwardly into the block.

The screw 50 may and preferably will engage a wire 57 inserted into a hole 58 in the block 48, to bind the same firmly be tween it and the walls of the hole and electrically connect the contact finger 33 with the wire 57, which is extended under the supporting piece or base 27 and connected to a binding post 59, at which connection may be made to the second point in the circuit to be tuned. The upper end of the block 48 is preferably provided with a recess 51 in which a coil spring 52 is received, and which latter. when the screw 50 is screwed down into the block, is placed under compression sufiicient to cause the washer 47 tofrictionally engage the under surface of the collar 46 with a relatively light pressureto exert a retarding etlecthpon the lateral movement of the pivoted arm while at the same time permitting the arm 14 to be moved laterally as the grooved end of the contact point or finger 3S follows around the successive coils lO of the helix. In addition, the coil spring 52 serves to yieldingly'hold the collar46 in engagement with the head of the screw 50, thus establishinga positive electrical connection at all times and under all conditions at this point. The pivotal connection of the arm 14 at 45 permits the said arm to be moved'toward and away from the helix for the purpose of enabling the metal point or finger to be disengaged from any particular coil of the helix and quickly moved axially of the'helix to engage a diil erent coil. The arm 14 may be provided with an insulating knob 60 for cnablingthe operator to lift the pivoted arm for this purpose. In addition, the knob 60 serves as a weight to hold the metal contact pointor finger 38 in light but firm engagement with the helix.

The cylinder or drum 20 may be rotated 'by hand,-and for this purpose an insulating lniob' 62 is secured. upon the extended end'of one of the bolts or shafts 22 of the drum 20, and as the latter is rotated, the entire length of a coil of the helix is engaged with the contact member or finger 33 for each revolution of the drum, and as the latter is ro tated, every portion of the coil against which the contact member or finger 38 bears engaged with the latter, with the result that very sharp tuning is effected. The helion form of the coil causes the contact finger group of coils.

S3 to be moved axially with relation to the drum so as to bring the contact finger into engagement with successive coils of the helix.

In this manner the entire wire of each coil may be utilized to obtain an exact and sensitive tuning of the circuit and thus a large 'ange of adjustment is afforded between each winding or coil, whereas in tuning coils as heretofore constructed and known to me, each coil was either tapped at a single point in its periphery by a metal slider rubbing across the wires axially of the'coils, or by a plurality of wire taps, one foreach In the first instance the range of adjustment is from one coil to-the next, and in the second instance from one group of coils to the next group, intermediate thetaps not-utilizednor available for making a sensitive or extremely :accurate tuning. The advantages of the present construction of tuning coil over these prior constructions of tuning coils will therefore be apparent. The helical form of wire coil enables the contact member or finger to be moved axially of the drum in opposite directions.

One embodiment of the invention isherein shown and described, but it is not desired to limit the invention to the particular construction shown.

Having thus described the invent-ion, what is claimed is:

1. A tuning coil for radio receiving apparatus, comprising a supporting base, a drum rotatably mounted thereon, a helix of conducting material upon the drum, and a contact: member co-operating with the helix comprising an arm mounted upon the supporting base to-xhave pivotal movement axially of the helix and toward and away from the helix.

2. A tuning coilifor-radio receiving apparatus, comprising a supporting base, a drum rotatably mounted thereon, a helix of conducting material upon: the drum, a contact member co-operating with the helix comprising an arm mounted upon the supporting base to have pivotal movement both axially of the helix and toward and away from' the helix, and means for frictionally restraining the axial pivotal movement of said contact member.

3. A tuning coil for radio receiving ap-- paratus, connn'ising a supportingibase, a drum rotatably mounted thereon, ahelix of conducting material upon the drum and a contact arm co-operating with said helix, a collar rotatably :mounted on said base and to which the contact arm is pivoted to move toward and away from said drum, and a spring co-operating with said collar.

4. A tuning coil for radio receiving apparatus comprising a. rotatable helix of con ductingmaterial, and means for mounting a contact member co-operating*therewith,

Ill

said contact member being capable of movement axially of the helix by rotation of the latter and of movement toward and away from said helix to be engaged With and disengaged therefrom and to be manually moved axially of the helix.

5. A tuning coil for radio receiving apparatus, comprising a supporting base, a drum rotatably mounted thereon, a helix of 10 conducting material upon the drum, and a contact member cooperating withthe helix comprising an arm mounted upon the supporting base to have pivotal movement both axially of the helix and toward and away from the helix, and a grooved metal finger carried by the arm and straddling one of the convolutions of the helix.

In testimony whereof, I have signed my name to this specification.

HENRY CORMACK. 

